Light emitting element type displays (light emitting devices) in which light emitting elements, such as organic EL elements, inorganic EL elements, or LEDs, are arranged in a matrix and the light emitting elements emit light for display are known.
The light emitting element type displays have excellent properties such as high luminance, high contrast, high resolution, and low power. Particularly, light emitting element type displays using organic EL elements have been drawing attention.
Among light emitting devices having at their pixels light emitting elements consisting of organic EL elements, some light emitting devices have at their pixels light emitting elements consisting of organic EL elements and drive elements such as thin film transistors for driving the light emitting elements, wherein the voltage applied to the pixels via data lines is controlled so as to control the current flowing through the organic EL elements and achieve light emission with a desired luminance.
Light emitting elements consisting of organic EL elements emit light as a current flows and it is known that they deteriorate in light emission properties over time in the course of light emission; consequently, resistance increases and luminous efficiency drops.
For that reason, when the same voltage is applied, the current flowing through the organic EL elements gradually decreases over time and the luminance drops. Then, after prolonged use of the light emitting device, the luminance for the same applied voltage gradually drops over time. When such a light emitting device is used in a display device, the images displayed according to image data gradually become darker and the display quality progressively drops.
With regard to the above problem, for example, Japanese Patent Application KOKAI Publication No. 2009-244654 describes a compensation circuit compensating change in the current flowing through organic EL elements.
The compensation circuit described in the Japanese Patent Application KOKAI Publication No. 2009-244654 passes a constant current to the light emitting elements, measures the voltage between the terminals of a light emitting element at that time, and corrects the voltage applied to the pixels based on the measured voltage so that the luminance in the initial properties is obtained regardless of deterioration over time.
However, the structure described in the Japanese Patent Application KOKAI Publication No. 2009-244654 requires the driver to have a constant current circuit for passing a constant current to the data lines; the driver is complex in circuit structure and control.